feat(nodes): move all invocation metadata (type, title, tags, category) to decorator

All invocation metadata (type, title, tags and category) are now defined in decorators.

The decorators add the `type: Literal["invocation_type"]: "invocation_type"` field to the invocation.

Category is a new invocation metadata, but it is not used by the frontend just yet.

- `@invocation()` decorator for invocations

```py
@invocation(
    "sdxl_compel_prompt",
    title="SDXL Prompt",
    tags=["sdxl", "compel", "prompt"],
    category="conditioning",
)
class SDXLCompelPromptInvocation(BaseInvocation, SDXLPromptInvocationBase):
    ...
```

- `@invocation_output()` decorator for invocation outputs

```py
@invocation_output("clip_skip_output")
class ClipSkipInvocationOutput(BaseInvocationOutput):
    ...
```

- update invocation docs
- add category to decorator
- regen frontend types

invokeai/frontend/web/src/features/nodes/types/types.ts

@@ -678,6 +678,7 @@ export type TypeHints = {
 export type InvocationSchemaExtra = {
   output: OpenAPIV3.ReferenceObject; // the output of the invocation
   title: string;
+  category?: string;
   tags?: string[];
   properties: Omit<
     NonNullable<OpenAPIV3.SchemaObject['properties']> &